|Title||Deglacial water-table decline in Southern California recorded by noble gas isotopes|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||Seltzer A.M, Ng J., Danskin W.R, Kulongoski JT, Gannon R.S, Stute M., Severinghaus JP|
|Type of Article||Article|
|Keywords||air; climate; diffusion; firn; fractionation; polar ice; Science & Technology - Other Topics|
Constraining the magnitude of past hydrological change may improve understanding and predictions of future shifts in water availability. Here we demonstrate that water-table depth, a sensitive indicator of hydroclimate, can be quantitatively reconstructed using Kr and Xe isotopes in groundwater. We present the first-ever measurements of these dissolved noble gas isotopes in groundwater at high precision (<= 0.005 parts per thousand amu(-1); 1 sigma), which reveal depth-proportional signals set by gravitational settling in soil air at the time of recharge. Analyses of California groundwater successfully reproduce modern groundwater levels and indicate a 17.9 +/- 1.3 m (+/- 1 SE) decline in water-table depth in Southern California during the last deglaciation. This hydroclimatic transition from the wetter glacial period to more arid Holocene accompanies a surface warming of 6.2 +/- 0.6 degrees C (+/- 1 SE). This new hydroclimate proxy builds upon an existing paleo-temperature application of noble gases and may identify regions prone to future hydrological change.